Russia intensifies undersea spying as hidden sensors track UK nuclear sub fleet

By Robert Stanley | 2025-04-16

Russia is escalating its covert operations in the Atlantic by deploying spy submarines and specialized research vessels to plant underwater sensors near critical infrastructure in a bid to track the United Kingdom's nuclear submarine fleet, a report found.

The mission appears to focus on monitoring key communication and power cables that connect Britain to Europe, as well as the Nordic states and Baltic countries, many of which were once part of the Soviet Union, British newspaper The Times reported April 5 following a three-month investigation.

The Royal Navy found some devices planted on the seabed while several washed ashore, the newspaper reported.

Military and intelligence chiefs say they were planted to gather intelligence on the United Kingdom's four submarines that carry nuclear missiles.

British officials liken the latest Russian activities to the Cold War-era technological race that pitted the United States against the Soviet Union for undersea dominance.

The battle for supremacy beneath the waves is intensifying, they warn.

"There should be no doubt, there is a war raging in the Atlantic," an unidentified senior British military officer told The Times. "This is a game of cat and mouse that has continued since the ending of the Cold War, and is now heating up again."

"We are seeing phenomenal amounts of Russian activity," the officer added.

Hunting Russian devices

Russian Ambassador to the United Kingdom Andrey Kelin did not deny the allegations that Russia is using sensors to track UK nuclear submarines.

At the same time, Kelin rejected the idea that such activities presented a threat to the United Kingdom.

Asked on BBC One's Sunday with Laura Kuenssberg whether he objected to the claims, Kelin said: "No."

"I am not going to deny it, but I wonder whether we really have an interest in following all the British submarine with very old outdated nuclear warheads... all these threats are extremely exaggerated," he said April 13.

In response, Britain has deployed the RFA Proteus, a specialized deep-sea surveillance vessel, to hunt for Russian surveillance devices, The Times reported.

The Proteus carries a submersible drone that can be lowered to the seafloor to detect hidden sensors and listening devices, which the British suspect are placed by Russian submarines and unmanned underwater vehicles (UUVs).

These sensors, positioned near vital data and energy cables, could enable Moscow to track and even neutralize the United Kingdom's strategic nuclear assets in a war, according to the report.

The United Kingdom's nuclear deterrent relies heavily on its four Vanguard-class submarines, which are designed to remain undetectable as they patrol the depths of the Atlantic.

These submarines, armed with nuclear-tipped ballistic missiles, form a critical part of NATO's strategy to deter Russian aggression.

However, Russia's increasing use of undersea sensors and drones could compromise their ability to remain hidden, potentially leaving Britain's deterrent vulnerable to tracking and destruction.

'Mother ship' submarines

What makes Russia's operations even more difficult to counter is the use of so-called mother ship submarines, The Times said. These vessels are capable of deploying autonomous UUVs deep below the sea, adding an additional layer of secrecy to their operations.

These covert submarines are designed to be difficult to detect, and the UUVs they deploy can travel long distances undetected while gathering critical intelligence or sabotaging undersea infrastructure.

The centerpiece of Russia's undersea research program is the Yantar, a sophisticated spy vessel that watchers have spotted off the coast of the United Kingdom multiple times, according to Janes, an open-source intelligence-gathering publication.

Equipped with two mini-submarines capable of diving to depths of up to 6,000 meters, the Yantar can map undersea infrastructure and plant surveillance devices on critical data cables, The Times report said.

The vessel's drones also are capable of cutting or manipulating undersea cables, a tactic that could disrupt vital communication and energy systems, it added.

Russia's shadow fleet

The disruption of undersea communication and power cables already has had real-world effects.

At least 11 cables have been severed since 2023. Vessels associated with Russia's shadow fleet -- unregistered ships often engaged in illicit activities like transporting Russian oil to sanctioned markets -- damaged several of them.

In response to these mounting threats, NATO has initiated a new defense system called Nordic Warden, which uses artificial intelligence and navy patrols to track Russia's shadow fleet, The Times reported.

Still, the threat is not just about surveillance.

There are concerns that Russia's undersea drones could target Britain's offshore wind farms, which supply almost 20% of the country's electricity, or even sever the vital cables that bring natural gas from Norway to the United Kingdom, it added.

As a precautionary measure, the Royal Navy has proposed creating a fleet of drones -- both surface and submersible -- to patrol the North Atlantic, particularly the area known as the GIUK Gap (Greenland, Iceland and the United Kingdom), according to the UK Defence Journal, a UK-based news website covering defense and security topics.